8 files changed, 34 insertions, 9 deletions
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 7d8e002c776..0303973822e 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202403291
+#define CATALOG_VERSION_NO	202403301
 
 #endif
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 1774c56ae31..e7ff8e4992f 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -544,9 +544,11 @@ typedef struct ResultRelInfo
 	/* ON CONFLICT evaluation state */
 	OnConflictSetState *ri_onConflict;
 
-	/* for MERGE, lists of MergeActionState */
-	List	   *ri_matchedMergeAction;
-	List	   *ri_notMatchedMergeAction;
+	/* for MERGE, lists of MergeActionState (one per MergeMatchKind) */
+	List	   *ri_MergeActions[3];
+
+	/* for MERGE, expr state for checking the join condition */
+	ExprState  *ri_MergeJoinCondition;
 
 	/* partition check expression state (NULL if not set up yet) */
 	ExprState  *ri_PartitionCheckExpr;
@@ -1401,6 +1403,13 @@ typedef struct ModifyTableState
 	/* For MERGE, the action currently being executed */
 	MergeActionState *mt_merge_action;
 
+	/*
+	 * For MERGE, if there is a pending NOT MATCHED [BY TARGET] action to be
+	 * performed, this will be the last tuple read from the subplan; otherwise
+	 * it will be NULL --- see the comments in ExecMerge().
+	 */
+	TupleTableSlot *mt_merge_pending_not_matched;
+
 	/* tuple counters for MERGE */
 	double		mt_merge_inserted;
 	double		mt_merge_updated;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b89baef95d3..a690ebc6e51 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -176,8 +176,6 @@ typedef struct Query
 								 * also USING clause for MERGE */
 
 	List	   *mergeActionList;	/* list of actions for MERGE (only) */
-	/* whether to use outer join */
-	bool		mergeUseOuterJoin pg_node_attr(query_jumble_ignore);
 
 	/*
 	 * rtable index of target relation for MERGE to pull data. Initially, this
@@ -187,6 +185,9 @@ typedef struct Query
 	 */
 	int			mergeTargetRelation pg_node_attr(query_jumble_ignore);
 
+	/* join condition between source and target for MERGE */
+	Node	   *mergeJoinCondition;
+
 	List	   *targetList;		/* target list (of TargetEntry) */
 
 	/* OVERRIDING clause */
@@ -1705,7 +1706,7 @@ typedef struct CommonTableExpr
 typedef struct MergeWhenClause
 {
 	NodeTag		type;
-	bool		matched;		/* true=MATCHED, false=NOT MATCHED */
+	MergeMatchKind matchKind;	/* MATCHED/NOT MATCHED BY SOURCE/TARGET */
 	CmdType		commandType;	/* INSERT/UPDATE/DELETE/DO NOTHING */
 	OverridingKind override;	/* OVERRIDING clause */
 	Node	   *condition;		/* WHEN conditions (raw parser) */
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 595eec2cbbd..0ab25d9ce7b 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -2372,6 +2372,8 @@ typedef struct ModifyTablePath
 	int			epqParam;		/* ID of Param for EvalPlanQual re-eval */
 	List	   *mergeActionLists;	/* per-target-table lists of actions for
 									 * MERGE */
+	List	   *mergeJoinConditions;	/* per-target-table join conditions
+										 * for MERGE */
 } ModifyTablePath;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 7f3db5105db..e025679f890 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -251,6 +251,8 @@ typedef struct ModifyTable
 	List	   *exclRelTlist;	/* tlist of the EXCLUDED pseudo relation */
 	List	   *mergeActionLists;	/* per-target-table lists of actions for
 									 * MERGE */
+	List	   *mergeJoinConditions;	/* per-target-table join conditions
+										 * for MERGE */
 } ModifyTable;
 
 struct PartitionPruneInfo;		/* forward reference to struct below */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 376f67e6a5f..aa727e722cc 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1875,10 +1875,18 @@ typedef struct BooleanTest
  *
  * Transformed representation of a WHEN clause in a MERGE statement
  */
+
+typedef enum MergeMatchKind
+{
+	MERGE_WHEN_MATCHED,
+	MERGE_WHEN_NOT_MATCHED_BY_SOURCE,
+	MERGE_WHEN_NOT_MATCHED_BY_TARGET
+} MergeMatchKind;
+
 typedef struct MergeAction
 {
 	NodeTag		type;
-	bool		matched;		/* true=MATCHED, false=NOT MATCHED */
+	MergeMatchKind matchKind;	/* MATCHED/NOT MATCHED BY SOURCE/TARGET */
 	CmdType		commandType;	/* INSERT/UPDATE/DELETE/DO NOTHING */
 	/* OVERRIDING clause */
 	OverridingKind override pg_node_attr(query_jumble_ignore);
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 7cc481b8c2d..c5c4756b0fc 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -283,7 +283,8 @@ extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
 												List *updateColnosLists,
 												List *withCheckOptionLists, List *returningLists,
 												List *rowMarks, OnConflictExpr *onconflict,
-												List *mergeActionLists, int epqParam);
+												List *mergeActionLists, List *mergeJoinConditions,
+												int epqParam);
 extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
 									Path *subpath,
 									Node *limitOffset, Node *limitCount,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 57514d064b7..6c959e85d54 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -414,6 +414,7 @@ PG_KEYWORD("skip", SKIP, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("smallint", SMALLINT, COL_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("snapshot", SNAPSHOT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("some", SOME, RESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("source", SOURCE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("sql", SQL_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("stable", STABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("standalone", STANDALONE_P, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -438,6 +439,7 @@ PG_KEYWORD("table", TABLE, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("target", TARGET, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("temporary", TEMPORARY, UNRESERVED_KEYWORD, BARE_LABEL)